Sourcing Iron Age softstone artefacts in southeastern Arabia: results from a programme of analysis...

Sourcing Iron Age softstone artefacts insoutheastern Arabia: results from a programmeof analysis using Inductively CoupledPlasma-Mass Spectrometry/Optical EmissionSpectrometry (ICP-MS/OES)

Introduction (1)Softstone artefacts are a common feature of archaeo-logical assemblages in southeastern Arabia from atleast the middle of the third millennium BC until therecent past. They are used as a fossile directeur for theidentificationof archaeological periods as theyappearto undergo systemic changes in decoration and formthrough these millennia. The parent geology fromwhich the rawmaterial comes ensures that they havea restricted origin, namely the al-Hajjar mountainrange. Nevertheless, softstone artefacts achieve a

wide distribution across southeastern Arabia andare found at nearly all coastal and desert sites (2). Inaddition, softstone vessels that appear comparable inform and morphology to those from southeasternArabia have been found at sites elsewhere in theNearEast, including Ur (3), Uruk (4), Haft Tepe (5), TepeYahya (6) and even Tell Fakhariyah in the SyrianJazirah (7). Closer to southeastern Arabia, numerousexamples have also been found in burials and settle-ment sites on Bahrain (8). As a traded item theyrepresent, therefore, the product of broader economic

Iron Age softstone vessels manufactured in southeastern Arabia are widelydistributed across that region and in lesser amounts throughout WesternAsia. Results from a pilot programme of analysis using Inductively CoupledPlasma Mass Spectrometry/Optical Emission Spectrometry on vessel frag-ments from two southeast Arabian sites are presented. These results indicatethe existence of geochemically distinct groups that are separated by bothtransition metals and rare earth elements. While this indicates the potentialfor the application of the provenance postulate in softstone analysis, thesepromising results need to be further tested by an expanded programme ofanalysis which includes quarry fragments.

Keywords: softstone, Iron Age, ICP, compositional analysis, rare earthelements, transition metals, southeastern Arabia

Peter Magee1, Don Barber2,Marta Sobur3 and SabahJasim4

1Department of Classical andNear Eastern Archaeology,Bryn Mawr College, USA;2Department of Geology,Bryn Mawr College, USA;3Department of Anthro-pology, Harvard University,USA; 4Sharjah ArchaeologicalMuseum, UAE

P. Magee

Dept. of Classical and Near EasternArchaeology

Bryn Mawr College

101 North Merion Avenue

Bryn Mawr PA 19010-2889

USA

E-mail: [email protected]

Arab. arch. epig. 2005: 16: 129–143 (2005)

Printed in Singapore. All rights reserved

129

processes that relate to both production and distribu-tion networks within southeastern Arabia and thewider Near East.

In ceramic studies, compositional analysis is nowcommonplace for examining such production sys-tems. For softstone analysis, however, compositionalor geochemical analysis is considered more prob-lematic as it has been argued that the sourcecomposition can be too heterogenic to permit theestablishment of an identifiable geochemical ‘finger-print’, the existence of which is the basis for theso-called ‘provenance postulate’.

In this paper, we present results from a pilotprogramme of analysis of Iron Age softstoneartefacts using Inductively Coupled Plasma-MassSpectrometry/Optical Emission Spectrometry (ICP-MS/OES). This project had two interrelated aims:firstly, we wish to revisit the applicability of aprovenance postulate for softstone artefacts bytesting internal homogeneity; secondly, we testedthe homogeneity of softstone at a regional level byanalysing groups of contemporary Iron Age artefactsfrom two sites that we consider were in economiccontact with each other during the Iron Age IIperiod.

Research backgroundBroadly speaking, softstone is a metamorphic rockcomposed of talc, chlorite, serpentine and otherminerals formed from the metasomatism of ultra-mafic rocks. Because of the variable nature ofalteration, both in terms of hydrothermal processand components, the composition of softstone candiffer significantly. Attempts to track the productionand movement of finished objects in this materialhave varied both in terms of methodology andsuccess. In the 1970s, Kohl, Harbottle and Sayreexamined a series of well-known softstone vesselsthat were widely distributed in the ancient Near Eastin the third millennium BC. That study focused onmineralogical analysis, in particular X-Ray Diffrac-tion (XRD) (9), and was able to highlight significantmineralogical differences between artefacts. Whencombined with quantitative archaeological analysis,an overview of trade during the Bronze Age wasposited (10). More recent work has highlightedmineralogical differences within sofstone artefactsfrom southeastern Arabia. Ziolkowski’s detailed

analysis of softstone artefacts from the burial siteof Sharm in the United Arab Emirates highlights atalc-rich group comprising talc (>95%), chlorite,rutile, clinozoisite and muscovite; and a chlorite-richgroup which comprised chlorite (>85%), muscovite,talc and clinozoisite. During the Iron Age both thesegroups were utilized but the chlorite-rich varietydominated, accounting for c. 80% of the assemblage(11). Chlorite was also identified as the most com-mon mineral in Iron Age softstone vessels from thesite of al-Thuqaibah in the al-Madam plain (12). Asnoted in that study, these results are in accordancewith the conclusions reached by David in a broadermineralogical study of Bronze Age softstone vessels(13).

Bulk compositional analysis has not, however,been systemically applied within the Near Easterncontext because of the assumption that softstone wastoo heterogenic. An exception is the study ofsoftstone vessels from the site of al-Thuqaibah. Inthat study, two vessels were analysed with X-RayFluorescence (XRF) and ICP. The data confirmed aSiO2, Al2O3, Fe2O3, (Cr, Ni) chemistry for the twoanalysed samples but only six trace and rare earthelements within that study had measurable quanti-ties (14).

Elsewhere in the Old World and in the NewWorld, Instrumental Neutron Activation Analysis(INAA) has been employed in an attempt to ascer-tain what analytes, if any, are potentially usefulelemental discriminators for softstone. A team ofresearchers led by Luckenbach employed INAA toaddress softstone sourcing in the northeastern Uni-ted States (15). They argued that sources could beidentified on the basis of Rare Earth Element (REE)abundance patterns. They contend that REE distri-bution patterns are consistent with those in theoriginal rock and are unaffected by process of‘steatization’ and metasomatic alteration. A focuson REE abundances was questioned by research onsteatite sources in Scotland that found high REEvariation within a single source and significantvariation between serpentine and adjacent alteredproducts such as steatite (16). Questions have beenraised, however, about the methodology of thatstudy and, in particular, the counting timesemployed for elemental abundance (17).

More recently, Truncer has further questioned areliance on REE alone and suggested that the

P. MAGEE ET AL.

130

transition metals have a greater potential to high-light meaningful geochemical differences betweensoftstone outcrops (18). In that study, researcherswere able to sample known prehistoric steatitequarries in the northeastern United States as wellas artefacts. The results of their study were positiveand they were able to geochemically differentiatesoftstone that came from several known quarriesand attribute artefacts to these groups. A focus onseven transition metals (Co, Cr, Fe, Sc, Zn, Mn andV) and aluminium made it possible to allocatesamples to a known source with an average successrate of 60% over eight quarries. They concluded that‘transition metals of the steatite samples analysedhere primarily represent compositional variation inthe parent material of the steatite sources’ (19). REEsalso contributed to the source differentiation in theirstudy and they noted that these may also reflect theparent rock from which the softstone or steatitederived. However, the ultramafic rock from whichsteatite derives is characteristically depleted in REE.The detection limits employed in their study and thefact that they were only able to obtain very smallsamples of steatite artefacts led them to concludethat ‘the contribution of REEs in separating steatitesources would most likely increase given a largehomogenized sample, but the large sample volumewould probably be prohibitively destructive in thecase of artefacts’ (20).

The present study was conceived of as a pilotprogramme to ascertain the applicability of geo-chemical studies for characterizing softstone arte-facts from southeastern Arabia. Given the relativehomogeneity of softstone vessel morphology anddesign during the Iron Age (21), it was hoped thatgeochemical differentiation of samples might pro-vide insights into the economic framework behindthe exchange of these vessels. Before embarking onlarge-scale sample collection and a costly pro-gramme of analysis, a pilot project was undertakento ascertain the potential of using element concen-tration data from ICP-MS/OES to chemically differ-entiate softstone artefacts.

Sites and samplingSamples were chosen from the sites of Muweilahand Jebel Buhais. Both sites are located in theEmirate of Sharjah, United Arab Emirates. Muweilah

is a settlement site located some 15 km from thepresent-day coast and about 45 km from the inlandal-Madam plain. The entire ancient settlement datesto the Iron Age II period. Numerous C14 dates, bothconventional and AMS, suggest that the site cameinto existence sometime towards the end of the tenthcentury BC and was destroyed after 800 but before600 BC. The ancient settlement consisted of camp-sites in the middle of which are several buildingssurrounded by a large fortification wall (22). Tradingin both local and foreign goods was probably theraison d’etre of the settlement with a wide range ofceramics, bronzes, and softstone and iron artefactsrecovered (23). None of the raw materials that werenecessary for the production of softstone artefactsare found within the environs of the settlement.

Jebel Buhais is one of a series of outcrops thatflank the western side of the al-Hajjar mountains.Excavations conducted in the 1980s revealed anumber of Iron Age tombs containing ceramic,bronze and softstone artefacts. Excavation by Span-ish archaeologists revealed an Iron Age II fortressthat is probably linked to the nearby settlement ofal-Thuqaibah. More recently, Dr. Sabah Jasim fromSharjah Archaeological Museum has been excava-ting at the site. So far, nearly 100 tombs dating to thethird, second and first millennia BC have beenexcavated. Softstone artefacts are plentiful in thesetombs. In associated habitation deposits evidence forthe production of softstone vessels has been noted,including half-finished vessels and partly-workedblocks (24). This suggests that production was takingplace near the site even if the most likely source ofthe raw material is the mountains to the east of JebelBuhais.

Iron Age softstone artefacts were chosen fromthese two sites in part because of the ease ofavailability, but also because they represent twosettlements that were integrated within a broadereconomic system during the Iron Age II period.During this period, there is a massive expansion ofsettlement (Fig. 1) in the inland piedmont oases as aresult of falaj or qanat technology, such as has beenfound at al-Thuqaibah near Jebel Buhais (25). At thesame time, the domestication of the camel permittedintensive cross-desert trade between the coast anddesert. Compositional data on ceramics fromMuweilah confirm that the settlement was receivingceramics from the inland oasis settlements, such as

SOURCING IRON AGE SOFTSTONE ARTEFACTS

131

those near al-Ain (26). Given a nearby source ofsoftstone and evidence of production at Jebel Buhais,and the absence of any nearby source at Muweilah,it is possible that trade in softstone vessels occurredbetween these two settlements (Fig. 2). In such ascenario Jebel Buhais, with its close proximity to themountains and evidence of softstone vessel manu-facture, would have played the role of supplier

while Muweilah, with its far-flung trade contacts,would have operated as an entrepot obtainingsoftstone from Jebel Buhais and other piedmont ormountains settlements.

Fifteen samples were analysed. Thirteen of thesewere from identifiable Iron Age vessel fragmentsfrom Jebel Buhais andMuweilah (Table 1, Figs 3–12).They are decorated in a consistent Iron Age style,

Fig. 1.

Major sites of the Iron Age II period in southeastern Arabia.

Fig. 2.

Satellite image showing the position of Muweilah, Jebel Buhais and the nearby al-Hajjar mountains.

P. MAGEE ET AL.

132

normally with horizontal and diagonal lines. Onefragment from Jebel Buhais (Fig. 9) is decorated in aslightly different manner. In addition to the normalIronAge formofdecoration it containeddot and circlemotifs that are normally associated with the Bronze

Age or Wadi Suq period (1900 to 1300 BC). Thistransitional style of decoration has been clarified inthe last few years and it seems likely that it dates toeither the Iron Age I (1300-1000 BC) or the Late WadiSuq period (1500-1300 BC) (27). The single fragmentcarries little statistic import but it was includedbecause the Late Wadi Suq and Iron Age I periodsrepresent a very different form of economic organ-ization in southeastern Arabia. Very few sedentarysettlements are known in this period and there is noevidence of either domesticated camel or falajirrigation (28). The possibility that this single artefactmay have come from a different source area, thusreflecting different lifeways, justified its inclusion inthe project.

Analysis of these fifteen samples set out to testtwo hypotheses that underpin any geochemicalprovenance analysis: 1) sample-to-sample (or inter-sample) geochemical variability is larger than withinsample (intra-sample) variability; and 2) geochemi-cal variability among potentially different popula-tions of samples (e.g. from different sites) is largerthan inter-sample variability. While neither of these

Table 1. Softstone samples. * ¼ duplicate samples.

Recording Code Site

Submission

Code Figure

2004/s2/m/ia Muweilah No. 1 3


2004/s5/m/ia Muweilah No. 3* 5

2004/s5/m/ia Muweilah No. 4* 5



2003/s1/bh/ia Jebel Buhais No. 7 8

2003/s9/bh/latewstrans Jebel Buhais No. 9* 9

2003/s9/bh/latewstrans Jebel Buhais No. 10* 9

2003/s6/bh/ia Jebel Buhais No. 11* 10

2003/s6/bh/ia Jebel Buhais No. 12*

2003/s3/bh/ia Jebel Buhais No. 13

2003/s5/bh/ia Jebel Buhais No. 14 11



Fig. 3.

Iron Age softstone sample No. 1.


133

Fig. 5.

Iron Age softstone sample No. 3/4.

Fig. 4.


P. MAGEE ET AL.

134

Fig. 7.


Fig. 6.



135

Fig. 9.

Late Wadi Suq-Iron Age transitional softstone sample Nos 9/10.

Fig. 8.


P. MAGEE ET AL.

136

Fig. 11.


Fig. 10.

Iron Age softstone sample No. 11/12.


137

tests can conclusively prove that the actual source-quarry sites can be uniquely identified, if eitherturns out to be false, then geochemical source-tracing would be futile. To assess the second aim wedouble-sampled four softstone artefacts (Nos 3/4, 9/10, 11/12, 15/16). These were submitted as individ-ual samples to the laboratory and each was given aunique submission code.

Geochemical resultsThe analysis was conducted at ACTLABS (Toronto,Canada) using a metaborate-tetraborate fusion pre-paration. ICP-OES was used for the determination ofMajor Elements (Si, Fe, Mn, Mg, Ca, Na, K, Ti and P)and ICP-MS was used for Minor, Trace and REEdata (V, Cr, Co, Ni, Ga, Rb, Sr, Y, Cs, Ba, La, Ce, Sm,Eu, Gd, Dy, Ho, Yb, Lu, Hf, Th) (Table 2). Severalstandards were included in the analysis for accuracy(29). These included SY3 (Syenite), NIST 694 (West-ern Phosphate Rock), W2 Cert (Diabase), BIR-1(Basalt), GBW 07113 (Granite) and NBS 1633b (FlyAsh).

Major and trace elementsMeasurable concentrations for twenty-one majorand trace elements (excluding REE) were obtained(Table 2). Bivariate plots (Fig. 13) of both Mg and Feconcentrations and Mg/Si and Al/Si ratios addressboth hypotheses. In both plots, the duplicate sam-ples cluster closely together. Furthermore, the dupli-cates cluster within the broader patterning that isevident in both plots. Most of the Muweilah samplesare separated from the Jebel Buhais samples byhigher Mg concentrations. The only exceptions tothis are Samples 1 and 5. Both of these samplescontain higher concentrations of Fe and lowerconcentrations of Mg. No. 1 also contains lowerconcentrations of Al. None of the duplicate samplesoverlap the observed patterning, that is inter-samplegeochemical variability does not exceed what areclear inter-sample geochemical differences.

A further observation is possible on the relativehomogeneity of samples from each site. The Mg/Feratio (Fig. 13a, Table 3) of the Jebel Buhais examplesexhibit consistent ratios; their average ratio is 4.82with a very low coefficient of variation (0.81). The

Fig. 12.

Iron Age softstone sample Nos 15/16.

P. MAGEE ET AL.

138

Muweilah examples, on the other hand, are muchless consistent. As noted above, Jebel Buhais is closerto softstone sources in the al-Hajjar mountains andevidence for the production of vessels has beennoted at the site. Greater homogeneity in elementalconcentrations is consistent with a source product.This is an issue that we turn to in more detail below.

An analysis of the transition metals, highlightedby Truncer as potentially significant in softstonesourcing, also addresses both hypotheses. A ternaryplot (Fig. 14) of three transition metals (Cr, Sc and V)shows that the duplicate samples have littleT

able2.

non-REEElemen

taldataforsamples.

*¼

duplicate

samples.

SiO

2Al2O3

Fe2O3

MnO

MgO

CaO

TiO

2Y

Sc

Zr

VCr

Co

Ni

Ga

Sr

Sam

ple

%%

%%

%%

%ppm

ppm

ppm

ppm

ppm

ppm

ppm

ppm

ppm

128

.330

19.560

8.05

00.04

030

.740

0.19

00.23

1)1.00

058

.000

6.00

017

1.00

064

4.80

812

7.20

496

2.60

010

.927

10.877

228

.150

20.620

2.69

00.01

333

.800

0.08

00.28

3)1.00

051

.000

4.00

021

1.00

028

9.59

537

.194

606.59

05.36

211

.932

3*28

.440

20.890

3.44

00.01

033

.450

0.23

00.67

0)1.00

064

.000

6.00

045

0.00

023

50.000

49.118

1520

.000

5.05

313

.810

4*28

.300

20.790

3.33

00.00

933

.720

0.09

00.89

0)1.00

067

.000

7.00

052

4.00

023

80.000

49.792

1620

.000

5.03

06.65

2

527

.080

20.380

11.170

0.03

627

.690

0.37

00.36

39.00

048

.000

6.00

020

4.00

052

2.36

218

2.91

979

8.44

513

.580

202.98

7

627

.770

20.420

3.89

00.02

533

.920

0.17

00.19

1)1.00

060

.000

)1.00

010

7.00

057

0.87

568

.180

1400

.000

7.41

813

.228

727

.820

21.780

6.28

00.03

230

.770

0.22

00.26

66.00

057

.000

3.00

013

2.00

071

7.04

099

.406

1130

.000

6.98

42.45

0

9*28

.070

20.530

5.61

00.02

430

.880

1.54

00.31

210

.000

90.000

4.00

024

7.00

025

5.48

999

.735

924.40

18.60

627

.380

10*

27.840

20.520

5.63

00.02

531

.120

1.20

00.35

312

.000

96.000

5.00

024

4.00

028

2.93

410

1.97

494

3.17

48.73

220

.012

11*

27.920

21.130

7.18

00.02

330

.470

0.66

00.33

312

.000

78.000

3.00

025

1.00

010

8.73

312

2.41

890

2.48

010

.378

7.43

0

12*

27.900

21.140

7.46

00.02

430

.060

0.79

00.29

910

.000

76.000

7.00

025

7.00

090

.150

128.22

384

9.06

210

.545

10.225

1327

.890

22.000

4.96

00.01

731

.670

0.53

00.27

02.00

047

.000

4.00

019

7.00

090

.243

94.097

858.66

58.38

912

.289

1427

.930

21.100

7.05

00.02

330

.530

0.68

00.28

58.00

090

.000

3.00

026

2.00

084

.663

124.33

384

5.98

910

.402

11.051

15*

28.060

21.330

7.11

00.02

330

.320

0.60

00.34

413

.000

87.000

6.00

025

0.00

015

2.76

012

4.27

489

2.61

010

.183

7.19

4

16*

27.790

21.420

7.14

00.02

330

.230

0.72

00.29

912

.000

82.000

5.00

024

0.00

017

0.18

512

5.35

790

1.37

710

.036

11.210

Fig. 13.

a. Mg and Fe concentrations. b. Al/Si and Mg/Si ratios.


139

variation in their concentrations of these elements.Furthermore, clear geochemical differences are evi-dent in samples from each site. Exceptions are No. 7which is from Jebel Buhais but clusters with theMuweilah samples, and No. 2 which is closer to theJebel Buhais example. No. 5 is also pulled towardsthe Jebel Buhais samples by lower concentrations ofCr and higher concentrations of V.

Unlike the studies of Truncer et al. which workedwith a known quarry site to test source composition,this study is based on samples from two consumersites, even if one, Jebel Buhais, contains evidence ofraw material processing. There is no a priori reason,

therefore, to believe that the source compositionfrom either site would necessarily be unique. On thebasis of the transition metals, including iron, thereare however, near-systemic differences in the com-position of artefacts from each site and thesedifferences are greater than those observed withinsamples. These differences are near-systemic becauseNos 1, 5, 7, 2 are geochemically different from othersamples from the same site.

REE analysisREE data were initially considered disappointing asmany samples returned values that were belowdetection limits (Table 4). Given the mafic characterof the Omani Ophiolite it was expected that REEwould be depleted. Nevertheless, the REE dataaddress both hypotheses. Firstly, the duplicatesamples (Nos 3/4, 9/10, 11/12 and 15/16) displaysimilar measurable concentrations of all REE. In thecase of the Muweilah duplicate (Nos 3/4) REE werenot measurable, except for Ce on one duplicate.

Secondly, there is a correlation between archaeo-logical provenance and REE concentration. Of thefive softstone artefacts from Muweilah only one(No. 5) has detectable REE. The reverse is true forthe Jebel Buhais examples: only one of the sevenanalysed artefacts (Steat 13) has all REE elementalconcentrations below the detection limits. When theREE data are chondrite normalized (Fig. 15) theclustering in REE abundance is clear. No. 5 fromMuweilah, which we noted did not cluster with theMuweilah samples for some elements, has REEabundance that is very similar to the Jebel Buhaisexamples, if not slightly enriched in some of theLight REE. No. 7 from Jebel Buhais, which we notedabove clustered with the Muweilah samples on thebasis of V, Sc and Cr, has REE abundances that arelower than the other examples from Jebel Buhais andNo. 5 from Muweilah. It also does not contain themarked negative Eu anomaly that characterizes thelatter samples.

There is significant similarity in REE abundancefor the Jebel Buhais samples. They are all LREEdepleted and, except for a marked negative Euabundance, exhibit no anomalous elemental con-centrations. Tentative comparisons can be madebetween the softstone geochemical data andthat published for various unmetamorphosed andmetamorphic ultramafic rocks in the region (30).

Table 3. Mg/Fe ratios * ¼ duplicate samples

SAMPLE MgO Fe2O3 Mg/Fe

STEAT-01 30.74 8.05 3.82

STEAT-02 33.80 2.69 12.57

STEAT-03* 33.45 3.44 9.72

STEAT-04* 33.72 3.33 10.13

STEAT-05 27.69 11.17 2.48

STEAT-06 33.92 3.89 8.72

STEAT-07 30.77 6.28 4.90

STEAT-09* 30.88 5.61 5.50

STEAT-10* 31.12 5.63 5.53

STEAT-11* 30.47 7.18 4.24

STEAT-12* 30.06 7.46 4.03

STEAT-13 31.67 4.96 6.39

STEAT-14 30.53 7.05 4.33

STEAT-15* 30.32 7.11 4.26

STEAT-16* 30.23 7.14 4.23

Fig. 14.

Ternary plot of V, Sc and Cr.

P. MAGEE ET AL.

140

This indicates that despite the obvious strong influ-ence of metasomatism, the geochemical signature ofthe parent rock is discernible for some of themeasured elements. Contrary to the findings ofMoffat and Butler, the REEs are therefore one groupof elements that might reflect the geochemistry ofthe protolith from which the softstone derived.

DiscussionThe majority of samples from both Muweilah andJebel Buhais are geochemically distinct. In explain-

ing this, we are mindful that source composition isonly one contributing factor to artefact composition.Studies in the compositional analysis of ceramicshave highlighted anthropogenic factors, such as theaddition of temper, as being of critical importance ingeochemical composition. Obviously for softstoneartefacts this is not an issue. However, the differentuses of softstone can also conceivably alter itschemical composition. Studies have shown thatcooking with steatite vessels can result in low-levelmigration of elements, particularly Mg, Fe and Mn,into prepared foodstuffs (31). Indeed, the artefactsfrom Muweilah and Jebel Buhais have very differentbiographies: those from Jebel Buhais were placedinto tombs, perhaps shortly after manufacture, whilethose from Muweilah were used in domestic con-texts, perhaps for several generations. However,there is no evidence that the softstone vessels fromMuweilah were used for cooking, so this is unlikelyto be a contributing factor to their geochemicalcomposition.

Post-depositional effects have also been highligh-ted as contributing to the final geochemistry ofartefacts (32). Artefacts from Muweilah were depos-ited in a matrix consisting of a burnt archaeologicaldeposit containing organic remains and coveredwith sand. The proximity of an ancient lagoonensured a relatively saline environment. The JebelBuhais artefacts were placed in tombs which were

Table 4. Rare Earth Element Concentrations (ppm). BDL ¼ below detection limits. * ¼ duplicate samples

Sample ID: La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

Detection Limits

(http://www.actlabs.com/

methsub_code4lithre.htm)

.05 .05 .01 .05 .01 .005 .01 .01 .01 .01 .01 .005 .01 .002

1 BDL 0.2 BDL 0.1 BDL BDL BDL BDL BDL BDL BDL BDL BDL BDL

2 BDL BDL BDL BDL BDL BDL BDL BDL BDL BDL BDL BDL BDL BDL

3* BDL 0.1 BDL BDL BDL BDL BDL BDL BDL BDL BDL BDL BDL BDL

4* BDL BDL BDL BDL BDL BDL BDL BDL BDL BDL BDL BDL BDL BDL

5 0.3 1.5 0.37 3.0 1.3 0.28 1.8 0.3 2.0 0.4 1.1 0.17 0.9 0.12

6 BDL BDL BDL BDL BDL BDL BDL BDL BDL BDL BDL BDL BDL BDL

7 0.1 0.4 0.09 0.9 0.5 0.19 0.8 0.2 1.2 0.2 0.7 0.09 0.5 0.05

9* 0.3 1.3 0.28 2.0 0.9 0.25 1.4 0.3 2.1 0.4 1.3 0.19 1.0 0.14

10* 0.3 1.4 0.32 2.1 1.0 0.29 1.5 0.3 2.3 0.5 1.4 0.20 1.1 0.15

11* 0.3 1.3 0.28 2.2 1.1 0.22 1.7 0.4 2.6 0.5 1.5 0.21 1.1 0.14

12* 0.3 1.1 0.24 1.6 0.8 0.20 1.3 0.3 1.9 0.4 1.1 0.16 0.9 0.12

13 BDL 0.2 BDL 0.2 BDL BDL 0.1 BDL 0.3 BDL 0.2 BDL 0.2 BDL

14 0.3 1.1 0.22 1.5 0.8 0.18 1.2 0.3 1.8 0.4 1.0 0.15 0.8 0.11

15* 0.4 1.4 0.30 2.2 1.1 0.23 1.8 0.4 2.7 0.5 1.6 0.22 1.2 0.15

16* 0.3 1.1 0.25 1.9 1.0 0.19 1.7 0.4 2.5 0.5 1.4 0.20 1.1 0.13

Fig. 15.

REE abundance after chrondrite normalization.


141

covered with alluvial debris from nearby limestoneoutcrops. In ceramic analysis these different envi-ronment types have been highlighted as altering anartefact’s geochemistry (33). However, the elementshighlighted in such studies are not those consideredas critical analytes in this project. Furthermore, thestructure of softstone is vastly different from firedceramic and it remains to be demonstrated that theformer is as open to post-depositional geochemicalalteration as the latter.

It would seem very unlikely, therefore, that thedifferences observed in softstone artefacts fromMuweilah and Jebel Buhais resulted from a post-manufacture or post-depositional process. Our pilotdata results are, therefore, compatible with both ofour previously stated hypotheses, i.e. 1) pairedanalyses of single artefacts show that intra-samplevariability is small relative to inter-sample variabil-ity; and 2) the geochemical data define sampleclusters that are distinguishable beyond the inter-sample variability. Furthermore, similarity of thesoftstone geochemistry with published whole-rockgeochemical data suggests that an expanded studymay allow much tighter constraints to be placed onpotential softstone sources, and indeed that geo-chemical analyses could tie samples with possiblesource-quarry sites.

The archaeological implications of this pilot studyare necessarily limited by the restricted number of

samples. However, the relative homogeneity of theJebel Buhais samples vs the relative heterogeneity ofthe Muweilah samples concurs with our broaderunderstanding of the functions of these sites. JebelBuhais is close to softstone sources and wasinvolved in softstone vessel production. Muweilahis a redistribution and trade site and one wouldexpect it to be receiving goods from many differentproduction centres.

Clearly, it is too early to start speaking about theexploitation of several geochemically identifiablesoftstone sources in Iron Age southeastern Arabia.Nevertheless, the results obtained in this pilotproject suggest that different sources were beingexploited during this period and that productionand trade of vessels made from these sources wereembedded within the broader economy of theregion. This very tentative conclusion can only beconfirmed by a more detailed study which includesmany more samples. Ideally, this would incorpor-ate material from known quarries but should alsoinclude materials from adjacent regions from whichcomparable softstone vessels have been published.For this purpose, researchers at Bryn Mawr Collegehave commenced obtaining samples from othersites in the United Arab Emirates and will bereporting on the results of that analysis in thefuture.

References1. The research presented in this paper

was conducted with funds provided

by Bryn Mawr College. A Hanna Hol-

born Gray undergraduate student fel-

lowship permitted Ms. Marta Sobur to

play a key role in the research project.

A version of this paper was presentedat a softstone study day at the British

Museum in July, 2004. We would like

to thank Dr. St John Simpson for

inviting one of us (PM) to attend that

function. Previous drafts of this paper

were read and commented upon by

Dr. Lloyd Weeks (University of Not-

tingham) who made many useful

comments. Any errors remain the

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Sourcing Iron Age softstone artefacts in southeastern Arabia: results from a programme of analysis...

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